NASA discovers 715 new planets

By Doug Gross, CNN

Updated 7:59 AM ET, Fri February 28, 2014

Photos: Where life might live beyond Earth10 photos

Where life might live beyond Earth – A team of astronomers announced April 17, 2014, that they have discovered the first Earth-size planet orbiting a star in the so-called "habitable zone" -- the distance from a star where liquid water might pool on the surface. That doesn't mean this planet has life on it, says Thomas Barclay, a scientist at the Bay Area Environmental Research Institute at Ames and a co-author of a paper on the planet, called Kepler-186f. He says the planet can be thought of as an "Earth-cousin rather than an Earth-twin. It has many properties that resemble Earth." The planet was discovered by NASA's Kepler Space Telescope. It's located about 500 light-years from Earth in the constellation Cygnus. The picture above is an artist's concept of what it might look like.

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Photos: Where life might live beyond Earth10 photos

Where life might live beyond Earth – Scientists announced in June 2013 that three planets orbiting star Gliese 667C could be habitable. This is an artist's impression of the view from one of those planets, looking toward the parent star in the center. The other two stars in the system are visible to the right.

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Where life might live beyond Earth – This diagram shows the planets thought to orbit star Gliese 667C, where c, f, and e appear to be capable of having liquid water. The relative sizes, but not relative separations, are shown to scale.

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Where life might live beyond Earth – This diagram lines up planets recently discovered by Kepler in terms of their sizes, compared to Earth. Kepler-22b was announced in December 2011; the three Super-Earths were announced April 18, 2013. All of them could potentially host life, but we do not yet know anything definitive about their compositions or atmosphere.

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Where life might live beyond Earth – This illustration depicts Kepler-62e, a planet in the habitable zone of a star smaller and cooler than the sun. It is located about 1,200 light-years from Earth in the constellation Lyra.

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Where life might live beyond Earth – This illustration depicts Kepler 62f, a planet in the habitable zone of a star smaller and cooler than the sun, in the same system as Kepler 62e.

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Where life might live beyond Earth – This diagram compares the planets of our own inner solar system to Kepler-62, a five-planet system about 1,200 light-years from Earth. Kepler-62e and Kepler-62f are thought capable of hosting life.

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Where life might live beyond Earth – The planet Kepler-69c is located about 2,700 light-years from Earth in the constellation Cygnus. This is an illustration of the planet, which is the smallest yet found to orbit in the habitable zone of a sun-like star.

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Where life might live beyond Earth – This diagram compares the planets of our own inner solar system to Kepler-69, which hosts a planet Kepler-69c that appears to be capable of hosting life, in addition to planet Kepler-69b.

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Where life might live beyond Earth – This artist's illustration represents the variety of planets being detected by NASA's Kepler spacecraft.

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Story highlights

Four of 715 newly discovered planets may support Earth-like life

It's the biggest single discovery of planets in history

All were found in the first two years of the Kepler telescope's voyage

NASA expects next batch of data to reveal more habitable planets

Our galactic neighborhood just got a lot bigger. NASA on Wednesday announced the discovery of 715 new planets, by far the biggest batch of planets ever unveiled at once.

By way of comparison, about 1,000 planets total had been identified in our galaxy before Wednesday.

Four of those planets are in what NASA calls the "habitable zone," meaning they have the makeup to potentially support life.

The planets, which orbit 305 different stars, were discovered by the Kepler space telescope and were verified using a new technique that scientists expect to make new planetary discoveries more frequent and more detailed.

"We've been able to open the bottleneck to access the mother lode and deliver to you more than 20 times as many planets as has ever been found and announced at once," said Jack Lissauer, a planetary scientist at NASA's Ames Research Center in California.

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Launched in March 2009, the Kepler space observatory was the first NASA mission to find planets similar to Earth that are in, or near, habitable zones -- defined as planets that are the right distance from a star for a moderate temperature that might sustain liquid water.

Tuesday's planets all were verified using data from the first two years of Kepler's voyage, meaning there may be many more to come.

"Kepler has really been a game-changer for our understanding of the incredible diversity of planets and planetary systems in our galaxy," said Douglas Hudgins, a scientist with NASA's astrophysics division.

The new technique is called "verification by multiplicity," and relies in part on the logic of probability. Instead of searching blindly, the team focused on stars that the technique suggests are likely to have more than one planet in their orbit.

NASA says 95% of the planets discovered by Kepler are smaller than Neptune, which is four times as big as Earth.

One of them is about twice the size of Earth and orbits a star half the size of Earth's sun in a 30-day cycle.

The other three planets in habitable zones also are all roughly twice the size of Earth. Scientists said the multiplicity technique is biased toward first discovering planets close to their star and that, when further data comes in, they expect to find a higher percentage of new planets that could potentially have a life-supporting climate like Earth's.

"The more we explore the more we find familiar traces of ourselves amongst the stars that remind us of home," said Jason Rowe, a research scientist at the SETI Institute in Mountain View, California, and co-leader of the research team.